GSM clock GPS txco help

Alexander Chemeris alexander.chemeris at
Wed May 22 21:30:58 UTC 2013

Hi Will,

Thank you for the good news. Answering to your question, first please
update your UmTRX firmware and host side UHD:
 1. Update your UHD and umtrx_scripts from the git. Build UHD.
 2. Flash attached ZPU firmware to a UmTRX with the following command:
      ./ --addr= --fw=usrp2p_txrx_uhd.bin
 3. Power cycle UmTRX

Calibrate with GPS:
 1. Take your UmTRX outside to get GPS lock.
 2. When GPS acquires a lock, use '' utility without
parameters to read current VCTCXO DAC value in a loop.
 3. When the value stabilise (couple minutes after GPS acquires the
lock), write this value to EEPROM:
      ./usrp_burn_mb_eeprom --key tcxo-dac --val <YOUR_VAL>
 4. Now i should pickup the value from EEPROM on boot, so GPS is no
required unless you change ambient temperature considerably.

Note, that you should warm up your UmTRX for a while before
calibration, because it depends on the TCXO temperature.

Let me know if something goes wrong - I wasn't able to test
everything, as I don't have my UmTRX with me at the moment.

On Tue, May 21, 2013 at 9:50 PM, Will Hawkins
<hawkinsw at> wrote:
> Hey Alexander!
> Yesterday we took our umtrx outside to get the GPS lock for calibrating the
> tcxo voltage. There were some good outcomes and bad outcomes:
> The good:
> If you remember correctly, Dan could not associate to the umtrx with his
> Galaxy Nexus. After getting a GPS signal, Dan's phone could associate! So,
> great news.
> The bad:
> We attempted to record the calibrated tcxo dac values and had no luck. We
> booted the umtrx board connected via serial console to my laptop. I was able
> to see the boot messages and other output so I know the console was working.
> Once the board got a GPS lock, I assumed that I would see some tcxo DAC
> values printed to the console. Based on what you said last week, I was going
> to wait until those values stabilized and then use that output to flash into
> the eeprom. Unfortunately I did not see any output on the serial console.
> Then I thought that we could poll the umtrx (using UHD probe) for its tcxo
> dac values. Unfortunately it showed the default (2048) every time.
> Can you tell me what I'm doing wrong?
> Thanks!
> Will
> PS: CC'ing Dan since he's working this with me.

Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
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